Polarizing film with adhesive layer, and liquid crystal display device

ABSTRACT

Provided is a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus, the polarizing film with a pressure-sensitive adhesive layer being suppressed in brightness reduction and being excellent in durability. The polarizing film with a pressure-sensitive adhesive layer of the present invention includes a polarizer and a pressure-sensitive adhesive layer arranged on at least one side of the polarizer. A distance between the polarizer and the pressure-sensitive adhesive layer is 25 μm or less. The pressure-sensitive adhesive layer has an absorption peak in a wavelength band in the range of from 580 nm to 610 nm. The pressure-sensitive adhesive layer contains a compound X represented by the general formula (I) or the general formula (II).

TECHNICAL FIELD

The present invention relates to a polarizing film with a pressure-sensitive adhesive layer and a liquid crystal display apparatus.

BACKGROUND ART

In an image display apparatus or the like, because of its image-forming system, it is indispensable to arrange a polarizing element on each of both surfaces of a liquid crystal cell, and a polarizing film is generally bonded thereto. A pressure-sensitive adhesive is typically used at the time of the bonding of the polarizing film to the liquid crystal cell. In addition, at the time of the bonding of the polarizing film and the liquid crystal cell, the respective materials are typically brought into close contact with each other through the use of the pressure-sensitive adhesive for reducing the loss of light. In such case, a polarizing film with a pressure-sensitive adhesive layer formed by arranging a pressure-sensitive adhesive layer on one surface of a polarizing film in advance is generally used because the polarizing film with a pressure-sensitive adhesive layer has, for example, the following merit. A drying step is not needed for fixing the polarizing film.

In recent years, the image display apparatus has been required to achieve lightness and vividness (i.e., color gamut widening), and hence an organic EL display apparatus (OLED) has been attracting attention. However, a liquid crystal display apparatus has also been required to achieve color gamut widening. For example, as a method of widening the color gamut of the liquid crystal display apparatus, a method including laminating a polarizing film on a liquid crystal cell via a pressure-sensitive adhesive layer containing a coloring matter showing an absorption maximum wavelength in a specific wavelength range has been proposed (Patent Literatures 1 and 2). In the related art method, however, a problem of a reduction in brightness caused by the absorption of light by the pressure-sensitive adhesive layer, a problem with durability in which the color of the pressure-sensitive adhesive layer containing a coloring matter deteriorates over time, and the like occur.

CITATION LIST Patent Literature

[PTL 1] JP 2011-039093 A

[PTL 2] JP 2014-092611 A

SUMMARY OF INVENTION Technical Problem

The present invention has been made to solve the conventional problems, and a primary object of the present invention is to provide a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus, the polarizing film with a pressure-sensitive adhesive layer being suppressed in brightness reduction and being excellent in durability.

Solution to Problem

According to one embodiment of the present invention, there is provided a polarizing film with a pressure-sensitive adhesive layer, including: a polarizer; and a pressure-sensitive adhesive layer arranged on at least one side of the polarizer, wherein a distance between the polarizer and the pressure-sensitive adhesive layer is 25 μm or less, wherein the pressure-sensitive adhesive layer has an absorption peak in a wavelength band in a range of from 580 nm to 610 nm, and wherein the pressure-sensitive adhesive layer contains a compound x represented by the following general formula (I) or general formula (II):

in the formula (I),

R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₁ and R₂ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₃, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₂ and R₃ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₅ and R₆ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₁, R₂, R₃, R₄, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₆ and R₇ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₂, R₃, R₄, R₅, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₁ and R₂ form a saturated cyclic skeleton including 5 or 6 carbon atoms, R₅ and R₆ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₃, R₄, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), or

R₂ and R₃ form a saturated cyclic skeleton including 5 to 7 carbon atoms, R₆ and R₇ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₄, R₅, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b); and in the formula (II), R₄ and R₈ each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms.

In one embodiment, the polarizer is a polyvinyl alcohol-based polarizer.

In one embodiment, the polarizer and the pressure-sensitive adhesive layer are directly laminated.

In one embodiment, the polarizer has an oxygen permeability of 1 [cm³/(m²·24 h·atm)] or less.

In one embodiment, the pressure-sensitive adhesive layer has a thickness of 25 μm or less.

According to another embodiment of the present invention, there is provided an image display apparatus. The image display apparatus includes the polarizing film with a pressure-sensitive adhesive layer.

Advantageous Effects of Invention

According to the present invention, the polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of the image display apparatus, which is suppressed in brightness reduction and is excellent in durability, can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of a polarizing film with a pressure-sensitive adhesive layer according to one embodiment of the present invention.

FIG. 2 is a schematic sectional view of a polarizing film with a pressure-sensitive adhesive layer according to one embodiment of the present invention.

FIG. 3 is a schematic sectional view of a polarizing film with a pressure-sensitive adhesive layer according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Now, preferred embodiments of the present invention are described. However, the present invention is not limited to these embodiments.

A. Polarizing Film with Pressure-Sensitive Adhesive Layer

FIG. 1 is a schematic sectional view of a polarizing film with a pressure-sensitive adhesive layer according to one embodiment of the present invention. A polarizing film 100 with a pressure-sensitive adhesive layer of this embodiment includes a polarizer 10 and a pressure-sensitive adhesive layer 20 arranged on at least one side of the polarizer 10. A distance “x” between the polarizer 10 and the pressure-sensitive adhesive layer 20 is 25 μm or less. The pressure-sensitive adhesive layer has an absorption peak in a wavelength band in the range of from 580 nm to 610 nm. Such pressure-sensitive adhesive layer may be obtained by incorporating a predetermined coloring matter into a pressure-sensitive adhesive layer.

In the present invention, when the pressure-sensitive adhesive layer selectively absorbs light in a specific wavelength range (from 580 nm to 610 nm) and is suppressed in unneeded absorption in a wavelength range except the specific wavelength range through the use of a specific coloring matter to be described later (coloring matter represented by the general formula (I) or (II)), a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus and to an improvement in brightness thereof can be obtained. When the polarizing film with a pressure-sensitive adhesive layer of the present invention is used, the color gamut of the image display apparatus can be significantly widened without use of a high-cost technology (an organic EL technology or a quantum dot technology). In addition, when the distance “x” between the polarizer and the pressure-sensitive adhesive layer is set to 25 μm or less, the penetration of oxygen from the side surface of the polarizing film with a pressure-sensitive adhesive layer is suppressed, and hence the color deterioration (decomposition) of the coloring matter is suppressed. Thus, the color gamut widening can be stably maintained over time. The fact that the coloring matter having low durability is made usable in the polarizing film with a pressure-sensitive adhesive layer is one achievement of the present invention. The penetration of oxygen in the main surface thereof is suppressed by the polarizer (typically a polarizer including polyvinyl alcohol) and a substrate or an adherend.

The distance “x” between the polarizer and the pressure-sensitive adhesive layer is preferably 10 μm or less, more preferably 5 μm or less, particularly preferably 1 μm or less. When the distance falls within such range, the effect of the present invention becomes more significant.

FIG. 2 is a schematic sectional view of a polarizing film with a pressure-sensitive adhesive layer according to one embodiment of the present invention. In a polarizing film 100′ with a pressure-sensitive adhesive layer of this embodiment, the polarizer 10 and the pressure-sensitive adhesive layer 20 are directly laminated (i.e., the distance “x” is 0). With such configuration, the effect of the present invention becomes particularly significant.

FIG. 3 is a schematic sectional view of a polarizing film with a pressure-sensitive adhesive layer according to another embodiment of the present invention. In a polarizing film 100″ with a pressure-sensitive adhesive layer of this embodiment, another layer 30 is arranged between the polarizer 10 and the pressure-sensitive adhesive layer 20. The other layer 30 may be a single layer, or may be a plurality of layers. The total thickness of the other layer 30 corresponds to the distance “x”. The total thickness of the other layer is preferably 25 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less, particularly preferably 1 μm or less.

In one embodiment, as illustrated in each of FIG. 2 and FIG. 3, in the polarizing film with a pressure-sensitive adhesive layer of the present invention, a protective film 40 is arranged on the side of the polarizer 10 opposite to the pressure-sensitive adhesive layer 20. The protective film may be arranged on each of both sides of the polarizer.

In one embodiment, as illustrated in each of FIG. 2 and FIG. 3, in the polarizing film with a pressure-sensitive adhesive layer of the present invention, a substrate 50 is arranged on the side of the pressure-sensitive adhesive layer 20 opposite to the polarizer 10. In one embodiment, a separator to be arranged for protecting the pressure-sensitive adhesive layer is used as the substrate 50 until the polarizing film with a pressure-sensitive adhesive layer is used. In another embodiment, a glass film is used as the substrate 50. The polarizing film with a pressure-sensitive adhesive layer including the glass film is useful as a polarizing film to be arranged on the viewer side of an image display apparatus because the glass film functions as a protective material. In addition, when a flexible glass film is used, such polarizing film can be provided in a roll shape, and hence the production efficiency of the image display apparatus can be improved. In addition, when the glass film is arranged as described above, a polarizing film with a pressure-sensitive adhesive layer whose pressure-sensitive adhesive layer is particularly excellent in durability can be obtained. In still another embodiment, the substrate 50 may be an optical film, such as a retardation film. The substrate 50 is not limited to the above-mentioned form, and may be, for example, any appropriate resin film.

A-1. Pressure-Sensitive Adhesive Layer

As described above, the pressure-sensitive adhesive layer has an absorption peak in the wavelength band in the range of from 580 nm to 610 nm. The formation of such pressure-sensitive adhesive layer can provide a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus and to an improvement in brightness thereof. The absorption spectrum of the film may be measured with a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, product name: “U-4100”).

The ratio (A₅₄₅/A_(max)) of the absorbance A₅₄₅ of the peak of the pressure-sensitive adhesive layer at a wavelength of 545 nm to the absorbance A_(max) of the highest absorption peak of the pressure-sensitive adhesive layer at a wavelength of from 580 nm to 610 nm is preferably 0.13 or less, more preferably 0.12 or less, still more preferably 0.11 or less, particularly preferably 0.1 or less. When a pressure-sensitive adhesive layer having a small absorbance at a wavelength of 545 nm as described above is formed, a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus by absorbing light that is not needed for color representation can be obtained. In addition, the film hardly absorbs light emitted from a light source whose wavelength is around 545 nm at which a visibility is high, and hence can be suppressed in brightness reduction.

In the pressure-sensitive adhesive layer, the half width of the absorption peak in the wavelength range of from 580 nm to 610 nm is preferably 35 nm or less, more preferably 30 nm or less, still more preferably 25 nm or less, particularly preferably 20 nm or less. When the half width falls within such range, a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus can be obtained.

In one embodiment, the pressure-sensitive adhesive layer is free of an absorption peak in the range of from 530 nm to 570 nm. More specifically, the pressure-sensitive adhesive layer is free of an absorption peak having an absorbance of 0.1 or more in the range of from 530 nm to 570 nm. The formation of such pressure-sensitive adhesive layer can provide a polarizing film with a pressure-sensitive adhesive layer that can contribute to the widening of the color gamut of an image display apparatus.

In one embodiment, the pressure-sensitive adhesive layer further has an absorption peak in a wavelength band in the range of from 440 nm to 510 nm. That is, in this embodiment, the pressure-sensitive adhesive layer has absorption peaks in the wavelength bands in the ranges of from 440 nm to 510 nm and from 580 nm to 610 nm. With such configuration, the color mixing of red light and green light, and that of green light and blue light can be satisfactorily prevented. When the polarizing film with a pressure-sensitive adhesive layer configured as described above is applied to an image display apparatus, the color gamut of the image display apparatus can be widened, and hence bright and vivid image quality can be obtained. A pressure-sensitive adhesive layer having two or more absorption peaks as described above may be obtained by using a plurality of kinds of coloring matters.

The transmittance of the pressure-sensitive adhesive layer at an absorption peak is preferably from 0% to 80%, more preferably from 0% to 70%. When the transmittance falls within such range, the above-mentioned effect of the present invention becomes more significant.

The visible light transmittance of the pressure-sensitive adhesive layer is preferably from 30% to 90%, more preferably from 30% to 80%. When the visible light transmittance falls within such range, a polarizing film with a pressure-sensitive adhesive layer that can widen the color gamut of an image display apparatus while being suppressed in brightness reduction can be obtained.

The thickness of the pressure-sensitive adhesive layer is preferably from 1 μm to 100 μm, more preferably from 2 μm to 50 μm, still more preferably from 5 μm to 35 μm. In one embodiment, the thickness of the pressure-sensitive adhesive layer is 25 μm or less. When the thickness falls within such range, the penetration of oxygen from an end portion of the pressure-sensitive adhesive layer can be preferably prevented.

The pressure-sensitive adhesive layer may be formed from a pressure-sensitive adhesive composition containing a base polymer and a coloring matter.

(Base Polymer)

The kind of the base polymer is not particularly limited, and examples thereof include various polymers, such as a rubber-based polymer, a (meth)acrylic polymer, a silicone-based polymer, a urethane-based polymer, a vinyl alkyl ether-based polymer, a polyvinyl alcohol-based polymer, a polyvinylpyrrolidone-based polymer, a polyacrylamide-based polymer, and a cellulose-based polymer. The pressure-sensitive adhesive composition contains the base polymer as a main component. The main component refers to a component having the largest content out of the total solid content in the pressure-sensitive adhesive composition, and means, for example, a component accounting for more than 50 wt % (preferably 70 wt %) of the total solid content in the pressure-sensitive adhesive composition.

In one embodiment, a (meth)acrylic polymer is used as the base polymer. The (meth)acrylic polymer is preferred because the polymer is excellent in optical transparency, shows preferred wettability, preferred cohesiveness, and preferred pressure-sensitive adhesive characteristics, such as an adhesive property, and is excellent in weatherability and heat resistance.

In one embodiment, the (meth)acrylic polymer contains, as a monomer unit, an alkyl (meth)acrylate serving as a main component. The (meth)acrylate means an acrylate and/or a methacrylate. An example of the alkyl(meth)acrylate is an alkyl(meth)acrylate having a linear or branched alkyl group having 1 to 18 (preferably 3 to 9) carbon atoms. The alkyl (meth)acrylates may be used alone or in combination thereof.

An alkyl (meth)acrylate having an aromatic ring, such as phenoxyethyl (meth)acrylate or benzyl (meth)acrylate, may be used as the alkyl (meth)acrylate. Those alkyl (meth)acrylates are preferred from the viewpoints of, for example, pressure-sensitive adhesive characteristics, durability, the adjustment of a retardation, and the adjustment of a refractive index.

One or more kinds of copolymerizable monomers each having a polymerizable functional group having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, may be introduced into the (meth)acrylic polymer through copolymerization for the purpose of improving the adhesive property or heat resistance of the polymer. Specific examples of such copolymerizable monomer include: hydroxyl group-containing monomers, such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate; carboxyl group-containing monomers, such as (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride group-containing monomers, such as maleic anhydride and itaconic anhydride; a caprolactone adduct of acrylic acid; sulfonic acid group-containing monomers, such as styrenesulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers, such as 2-hydroxyethylacryloyl phosphate.

In addition, examples of the copolymerizable monomer for the purpose of modification also include: (N-substituted) amide-based monomers, such as (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, and N-methylolpropane (meth)acrylamide; alkylaminoalkyl (meth)acrylate-based monomers, such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylate-based monomers, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; succinimide-based monomers, such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyoctamethylenesuccinimide, and N-acryloylmorpholine; maleimide-based monomers, such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; and itaconimide-based monomers, such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide.

Further, as the monomer for modification (copolymerizable monomer), there may be used, for example: vinyl-based monomers, such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate-based monomers, such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers, such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers, such as polyethyleneglycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylic acid ester-based monomers, such as tetrahydrofurfuryl (meth)acrylate, fluorinated (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate. Examples thereof further include isoprene, butadiene, isobutylene, and vinyl ether.

Further, an example of the copolymerizable monomer except the above-mentioned monomers is a silane-based monomer containing a silicon atom. Examples of the silane-based monomer include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

In addition, as the copolymerizable monomer, there may also be used, for example: a polyfunctional monomer having two or more unsaturated double bonds, such as a (meth)acryloyl group or a vinyl group, for example, an esterified product of (meth)acrylic acid and a polyhydric alcohol, such as tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate; or a polyester (meth)acrylate, epoxy (meth)acrylate, or urethane (meth)acrylate obtained by adding two or more unsaturated double bonds, such as a (meth)acryloyl group or a vinyl group, serving as a functional group similar to that of a monomer component, to a skeleton of polyester, epoxy, or urethane.

In the (meth)acrylic polymer, the content of a constituent unit derived from the copolymerizable monomer is preferably from 0 parts by weight to 20 parts by weight, more preferably from 0.1 part by weight to 15 parts by weight, still more preferably from 0.1 part by weight to 10 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer.

In one embodiment, a hydroxyl group-containing monomer and/or a carboxyl group-containing monomer is used as the copolymerizable monomer. When the pressure-sensitive adhesive composition contains a cross-linking agent, any such copolymerizable monomer serves as a reaction point with the cross-linking agent. The hydroxyl group-containing monomer, the carboxyl group-containing monomer, or the like is rich in reactivity with an intermolecular cross-linking agent, and is hence preferably used for improving the cohesiveness or heat resistance of the pressure-sensitive adhesive layer to be obtained. The hydroxyl group-containing monomer is preferred in terms of the reworkability of the layer, and the carboxyl group-containing monomer is preferred in terms of the achievement of both of the durability and reworkability thereof.

When the hydroxyl group-containing monomer is used as the copolymerizable monomer, the content of a constituent unit derived from the hydroxyl group-containing monomer is preferably from 0.01 part by weight to 15 parts by weight, more preferably from 0.03 part by weight to 10 parts by weight, still more preferably from 0.05 part by weight to 7 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer. When the carboxyl group-containing monomer is used as the copolymerizable monomer, the content of a constituent unit derived from the carboxyl group-containing monomer is preferably from 0.05 part by weight to 10 parts by weight, more preferably from 0.1 part by weight to 8 parts by weight, still more preferably from 0.2 part by weight to 6 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer.

The weight-average molecular weight of the (meth)acrylic polymer is, for example, from 500,000 to 3,000,000. A (meth)acrylic polymer having a weight-average molecular weight of from 700,000 to 2,700,000 (more preferably from 800,000 to 2,500,000) is preferably used in consideration of its durability, in particular, heat resistance. The weight-average molecular weight refers to a value measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

Known production methods including solution polymerization, radiation polymerization, such as UV polymerization, bulk polymerization, emulsion polymerization, and various kinds of radical polymerization may each be appropriately selected for the production of the (meth)acrylic polymer. The (meth)acrylic polymer to be obtained may be any one of, for example, a random copolymer, a block copolymer, and a graft copolymer.

In the solution polymerization, for example, ethyl acetate or toluene is used as a polymerization solvent. The solution polymerization is performed by adding a polymerization initiator in a stream of an inert gas, such as nitrogen, under the reaction conditions of a temperature of from about 50° C. to about 70° C. and a time period of from about 5 hours to about 30 hours.

A polymerization initiator, a chain transfer agent, an emulsifying agent, or the like to be used in the radical polymerization is not particularly limited, and may be appropriately selected and used. The weight-average molecular weight of the (meth)acrylic polymer may be controlled by the usage amount of the polymerization initiator or the chain transfer agent, and reaction conditions, and the usage amount is appropriately adjusted in accordance with the kind thereof.

Examples of the radical polymerization initiator may include, but not limited to: azo-based initiators, such as 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis(2-methylpropionamidine) disulfate, 2,2′-azobis(N,N′-dimethyleneisobutylamidine), and 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057); persulfates, such as potassium persulfate and ammonium persulfate; peroxide-based initiators, such as di(2-ethylhexyl) peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexylperoxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; and redox-based initiators each formed by a combination of a peroxide and a reducing agent, such as a combination of a persulfate and sodium hydrogen sulfite and a combination of a peroxide and sodium ascorbate. The radical polymerization initiators may be used alone or as a mixture thereof.

The content of the radical polymerization initiator is preferably from 0.005 part by weight to 1 part by weight, more preferably from 0.02 part by weight to 0.5 part by weight with respect to 100 parts by weight of the monomer.

Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chain transfer agents may be used alone or as a mixture thereof. The content of the chain transfer agent is preferably 0.1 part by weight or less with respect to 100 parts by weight of the monomer.

In addition, examples of an emulsifying agent to be used in the emulsion polymerization include: anionic emulsifying agents, such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, an ammonium polyoxyethylene alkyl ether sulfate, and a sodium polyoxyethylene alkyl phenyl ether sulfate; and nonionic emulsifying agents, such as a polyoxyethylene alkyl ether, a polyoxyethylene alkyl phenyl ether, a polyoxyethylene fatty acid ester, and a polyoxyethylene-polyoxypropylene block polymer. Those emulsifying agents may be used alone or in combination thereof.

Further, as a reactive emulsifying agent, there is given, for example, an emulsifying agent obtained by introducing a radical polymerizable functional group, such as a propenyl group or an allyl ether group. Specific examples thereof include Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, and BC-20 (each of which is manufactured by DKS Co., Ltd.), and ADEKA REASOAP SE10N (manufactured by Asahi Denka Kogyo K.K.). The reactive emulsifying agent is preferred because the emulsifying agent is captured in the chain of the polymer after its polymerization, and hence the water resistance of the polymer is improved. The usage amount of the emulsifying agent is preferably from 0.3 part by weight to 5 parts by weight with respect to 100 parts by weight of the total amount of the monomer component, and is more preferably from 0.5 part by weight to 1 part by weight in terms of the polymerization stability and mechanical stability of the polymer.

(Coloring Matter)

The pressure-sensitive adhesive layer contains one or more kinds of coloring matters.

In one embodiment, the pressure-sensitive adhesive layer contains, as a coloring matter, a compound X represented by the following general formula (I) or general formula (II). The compound X is a compound having an absorption peak in the wavelength band in the range of from 580 nm to 610 nm.

in the formula (I),

R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₁ and R₂ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₃, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₂ and R₃ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₅ and R₆ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₁, R₂, R₃, R₄, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₆ and R₇ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₂, R₃, R₄, R₅, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R₁ and R₂ form a saturated cyclic skeleton including 5 or 6 carbon atoms, R₅ and R₆ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₃, R₄, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), or

R₂ and R₃ form a saturated cyclic skeleton including 5 to 7 carbon atoms, R₆ and R₇ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₄, R₅, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b); and in the formula (II), R₄ and R₈ each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms.

The saturated cyclic skeleton (number of carbon atoms: 5 or 6) formed so as to include R₁ and R₂, and the saturated cyclic skeleton (number of carbon atoms: 5 or 6) formed so as to include R₅ and R₆ may each have a substituent. The substituent is, for example, an alkyl group having 1 to 4 carbon atoms. In addition, the saturated cyclic skeleton (number of carbon atoms: 5 to 7) formed so as to include R₂ and R₃, and the saturated cyclic skeleton (number of carbon atoms: 5 to 7) formed so as to include R₆ and R₇ may each have a substituent. The substituent is, for example, an alkyl group having 1 to 4 carbon atoms.

In one embodiment, R₄ and/or R₈ has a benzene ring or a naphthalene ring as a substituent.

Specific examples of the compound X represented by the formula (I) or (II) include compounds represented by the following general formulae (I-1) to (I-27) and (II-1). The absorption peak of the compound X is shown in each of the following tables. With regard to each of the formulae (I-1) to (I-23), an absorption peak obtained by measuring the absorbance of a film formed of a resin composition prepared by mixing aliphatic polycarbonate with the compound X is shown, and with regard to each of the formulae (I-24) to (I-27) and (II-1), an absorption peak obtained by measuring the absorbance of a film formed of a resin composition prepared by mixing a polymethyl methacrylate resin with the compound X is shown.

Absorption peak NO. Compound X (nm) I-1

596 nm (APC) I-2

595 nm (APC) I-3

582 nm (APC) I-4

585 nm (APC) I-5

585 nm (APC) I-6

575 nm (APC) I-7

585 nm (APC) I-8

587 nm (APC) I-9

587 nm (APC) I-10

588 nm (APC) I-11

588 nm (APC) I-12

589 nm (APC) I-13

592 nm (APC) I-14

591 nm (APC) I-15

595 nm (APC) I-16

595 nm (APC) I-17

596 nm (APC) I-18

614 nm (APC) I-19

581 nm (APC) I-20

591 nm (APC) I-21

593 nm (APC) I-22

594 nm (APC) I-23

594 nm (APC) I-24

592 nm I-25

593 nm I-26

594 nm I-27

594 nm II-1

597 nm

The content of the compound X is preferably from 0.01 part by weight to 50 parts by weight, more preferably from 0.05 part by weight to 10 parts by weight, still more preferably from 0.1 part by weight to 5 parts by weight, particularly preferably from 0.1 part by weight to 1 part by weight with respect to 100 parts by weight of the base polymer.

The compound X is a compound that is typically difficult to use as an additive for an optical member because the compound has the following feature: the compound is liable to alter (its color is liable to deteriorate) under the influence of moisture, oxygen, or the like. According to the present invention, however, even when a pressure-sensitive adhesive layer containing the compound X is formed, the deterioration of the pressure-sensitive adhesive layer over time can be prevented.

The pressure-sensitive adhesive layer may further contain a compound having an absorption peak in the wavelength band in the range of from 440 nm to 510 nm. For example, an anthraquinone-based, oxime-based, naphthoquinone-based, quinizarin-based, oxonol-based, azo-based, xanthene-based, or phthalocyanine-based compound (dye) is used as such compound.

The content of the compound having an absorption peak in the wavelength band in the range of from 440 nm to 510 nm is preferably from 0.01 part by weight to 50 parts by weight, more preferably from 0.01 part by weight to 25 parts by weight with respect to 100 parts by weight of the base polymer.

(Additive)

The pressure-sensitive adhesive composition may contain a cross-linking agent. An organic cross-linking agent or a polyfunctional metal chelate may be used as the cross-linking agent. Examples of the organic cross-linking agent include an isocyanate-based cross-linking agent, a peroxide-based cross-linking agent, an epoxy-based cross-linking agent, and an imine-based cross-linking agent. The polyfunctional metal chelate is such that a polyvalent metal atom is covalently bonded or coordinated to an organic compound. Examples of the polyvalent metal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. An atom in the organic compound to which the polyvalent metal atom is covalently bonded or coordinated is, for example, an oxygen atom, and examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, and a ketone compound.

Examples of the isocyanate-based cross-linking agent may include: isocyanate monomers, such as tolylene diisocyanate, chlorophenylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate; isocyanate compounds each obtained by addition of those isocyanate monomers to trimethylolpropane or the like; isocyanurated products; biuret-type compounds; and urethane prepolymer-type isocyanates each obtained by an addition reaction with polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol. Of those, a polyisocyanate compound formed of one kind selected from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate, or a polyisocyanate compound derived therefrom is particularly preferred. Herein, examples of the polyisocyanate compound formed of one kind selected from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate, or the polyisocyanate compound derived therefrom include hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, a polyol-modified hexamethylene diisocyanate, a polyol-modified hydrogenated xylylene diisocyanate, a trimer-type hydrogenated xylylene diisocyanate, and a polyol-modified isophorone diisocyanate. Each of the exemplified polyisocyanate compounds is preferred because its reaction with a hydroxyl group rapidly advances through the use of, in particular, an acid or abase in the polymer like a catalyst, and hence contributes, in particular, to the fast cross-linking of the pressure-sensitive adhesive composition.

A peroxide having a 1-minute half-life temperature of from 80° C. to 160° C. is preferably used as the peroxide-based cross-linking agent from the viewpoints of its workability and stability, and a peroxide having a 1-minute half-life temperature of from 90° C. to 140° C. is more preferably used. Examples of the peroxide-based cross-linking agent include di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1° C.), di-sec-butyl peroxydicarbonate (1-minute half-life temperature: 92.4° C.), t-butyl peroxyneodecanoate (1-minute half-life temperature: 103.5° C.), t-hexyl peroxypivalate (1-minute half-life temperature: 109.1° C.), t-butyl peroxypivalate (1-minute half-life temperature: 110.3° C.), dilauroyl peroxide (1-minute half-life temperature: 116.4° C.), di-n-octanoyl peroxide (1-minute half-life temperature: 117.4° C.), 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate (1-minute half-life temperature: 124.3° C.), di(4-methylbenzoyl) peroxide (1-minute half-life temperature: 128.2° C.), dibenzoyl peroxide (1-minute half-life temperature: 130.0° C.), t-butyl peroxyisobutyrate (1-minute half-life temperature: 136.1° C.), and 1,1-di(t-hexylperoxy)cyclohexane (1-minute half-life temperature: 149.2° C.). Of those, di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1° C.), dilauroyl peroxide (1-minute half-life temperature: 116.4° C.), dibenzoyl peroxide (1-minute half-life temperature: 130.0° C.), or the like is preferably used because any such compound is particularly excellent in cross-linking reaction efficiency. The half-life of a peroxide is an indicator representing the decomposition rate of the peroxide, and refers to a time period required for the remaining amount of the peroxide to reduce by half. A decomposition temperature for obtaining a half-life in any time period and a half-life time at any temperature are described in a manufacturer catalog or the like, and are described in, for example, “Organic Peroxide Catalog, 9th Edition (May 2003)” by Nippon Oil & Fats Co., Ltd.

The content of the cross-linking agent is preferably 20 parts by weight or less, more preferably from 0.01 part by weight to 20 parts by weight, still more preferably from 0.03 part by weight to 10 parts by weight with respect to 100 parts by weight of the base polymer. When the content of the cross-linking agent is more than 20 parts by weight, a pressure-sensitive adhesive layer that does not have sufficient moisture resistance and is liable to peel in a reliability test or the like may be formed.

The pressure-sensitive adhesive composition may contain a silane coupling agent. The use of the silane coupling agent can improve the durability of the composition. Examples of the silane coupling agent include: epoxy group-containing silane coupling agents, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents, such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents, such as 3-acryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents, such as 3-isocyanatopropyltriethoxysilane. The silane coupling agents may be used alone or as a mixture thereof.

The content of the silane coupling agent is preferably from 0.001 part by weight to 5 parts by weight, more preferably from 0.01 part by weight to 1 part by weight, particularly preferably from 0.02 part by weight to 1 part by weight, most preferably from 0.05 part by weight to 0.6 part by weight with respect to 100 parts by weight of the base polymer. When the content falls within such range, a pressure-sensitive adhesive layer that is excellent in durability and moderately holds an adhesive strength to an optical member, such as a liquid crystal cell, can be formed.

The pressure-sensitive adhesive composition may contain a polyether-modified silicone. A polyether-modified silicone disclosed in, for example, JP 2010-275522 A may be used as the polyether-modified silicone.

The pressure-sensitive adhesive composition may contain any appropriate other additive. For example, powder, such as a colorant or a pigment, a dye, a surfactant, a plasticizer, a tackifier, a surface lubricating agent, a leveling agent, a softening agent, an age resistor, an antioxidant, a light stabilizing agent, a UV absorbing agent, a polymerization inhibitor, an inorganic or organic filler, metal powder, particles, or foil may be appropriately added in accordance with a use application.

The pressure-sensitive adhesive layer containing the coloring matter is formed from the pressure-sensitive adhesive composition. At the time of the formation of the pressure-sensitive adhesive layer, it is preferred that the influences of the cross-linking treatment temperature and cross-linking treatment time of the composition be sufficiently considered together with the adjustment of the addition amount of the cross-linking agent. The cross-linking treatment temperature and the cross-linking treatment time may be adjusted by the cross-linking agent to be used. The cross-linking treatment temperature is preferably 170° C. or less. In addition, the cross-linking treatment of the composition may be performed at a temperature at the time of a step of drying the pressure-sensitive adhesive layer, or may be performed by separately arranging a cross-linking treatment step after the drying step. In addition, the cross-linking treatment time, which may be set in consideration of productivity and workability, is typically from about 0.2 minute to about 20 minutes, preferably from about 0.5 minute to about 10 minutes.

The pressure-sensitive adhesive layer is produced by, for example, a method including applying the pressure-sensitive adhesive composition to a separator, drying and removing the polymerization solvent or the like to form the pressure-sensitive adhesive layer, and then transferring the layer onto a polarizing film, or a method including applying the pressure-sensitive adhesive composition to the polarizing film, and drying and removing the polymerization solvent or the like to form the pressure-sensitive adhesive layer on the polarizer film. At the time of the application of the pressure-sensitive adhesive composition, one or more kinds of solvents except the polymerization solvent may be appropriately added anew.

A release-treated separator is preferably used as the separator, and for example, a silicone release liner is preferably used.

Any appropriate method may be used as a method of applying the pressure-sensitive adhesive composition. Specific examples thereof include methods using roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and an extrusion coating method using a die coater or the like.

An appropriate method may be appropriately adopted as a method of drying the pressure-sensitive adhesive composition in accordance with a purpose. A method including heating and drying the applied film of the composition is preferably used. The temperature at which the applied film is heated and dried is preferably from 40° C. to 200° C., more preferably from 50° C. to 180° C., particularly preferably from 70° C. to 170° C. When the heating temperature is set within the range, a pressure-sensitive adhesive having an excellent pressure-sensitive adhesive characteristic can be obtained. Any appropriate time may be adopted as the drying time of the applied film. The drying time is preferably from 5 seconds to 20 minutes, more preferably f rom 5 seconds to 10 minutes, particularly preferably from 10 seconds to 5 minutes.

In addition, an anchor layer (having a thickness of, for example, from about 0.5 μm to about 2 μm) may be formed on the surface of the polarizer film, or the pressure-sensitive adhesive layer may be formed after the surface has been subjected to various easy-adhesion treatments, such as a corona treatment and a plasma treatment. In addition, the surface of the pressure-sensitive adhesive layer may be subjected to an easy-adhesion treatment.

A-2. Polarizer and Protective Film

Any appropriate polarizer is used as the polarizer. Examples thereof include polyene-based alignment films, such as: a product obtained by causing a hydrophilic polymer film, such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film, to adsorb a dichroic substance, such as iodine or a dichroic dye, and uniaxially stretching the resultant; a dehydration-treated product of polyvinyl alcohol; and a dehydrochlorination-treated product of polyvinyl chloride. Of those, a polarizer obtained by causing the polyvinyl alcohol-based film to adsorb the dichroic substance, such as iodine, and uniaxially stretching the resultant (also referred to as “polyvinyl alcohol-based polarizer”) is particularly preferred because of its high polarization dichroic ratio. In addition, the polyvinyl alcohol-based polarizer is advantageous because of its low oxygen permeability. The oxygen permeability of the polarizer is preferably 1 [cm³/(m²·24 h·atm)] or less. The thickness of the polarizer is preferably from 0.5 μm to 80 μm. The oxygen permeability may be measured under the conditions of 23° C. and 0% RH in conformity with JIS K 7126-2.

The polarizer obtained by causing the polyvinyl alcohol-based film to adsorb iodine and uniaxially stretching the resultant is typically produced by: immersing polyvinyl alcohol in an aqueous solution of iodine to dye the polyvinyl alcohol; and stretching the dyed polyvinyl alcohol so that the polyvinyl alcohol may have a length 3 to 7 times as long as its original length. The stretching may be performed after the dyeing, the stretching may be performed while the dyeing is performed, or the dyeing may be performed after the stretching. The polarizer is produced through a treatment, such as swelling, cross-linking, adjustment, water washing, or drying, in addition to the stretching and the dyeing. For example, when the polyvinyl alcohol-based film is washed with water by being immersed in the water before the dyeing, contamination and an antiblocking agent on the surface of the polyvinyl alcohol-based film can be washed off. Moreover, the polyvinyl alcohol-based film can be swollen to prevent its dyeing unevenness or the like. The polyvinyl alcohol-based film may be a single-layer film (typical film-formed film), or may be a polyvinyl alcohol-based resin layer applied and formed onto a resin substrate. A technology involving producing a polarizer from the single-layer polyvinyl alcohol-based film is well-known in the industry. A technology involving producing a polarizer from the polyvinyl alcohol-based resin layer applied and formed onto the resin substrate is described in, for example, JP 2009-098653 A.

The polarizer preferably shows absorption dichroism at any wavelength in the wavelength range of from 380 nm to 780 nm. The single layer transmittance of the polarizer is preferably from 38% to 45.5%, more preferably from 40% to 45%.

The polarization degree of the polarizer is preferably 99.9% or more, more preferably 99.95% or more.

Any appropriate film may be used as the protective film. A material serving as a main component of such film is, specifically, for example, a cellulose-based resin, such as triacetyl cellulose (TAC), or a transparent resin, such as a (meth)acrylic, polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, or acetate-based resin. Another example thereof is a thermosetting resin or a UV-curable resin, such as an acrylic, urethane-based, acrylic urethane-based, epoxy-based, or silicone-based resin. Still another example thereof is a glassy polymer, such as a siloxane-based polymer. In addition, a polymer film described in JP 2001-343529 A (WO 01/37007 A1) may also be used. For example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain thereof, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group inside chains thereof may be used as a material for the film, and the resin composition is, for example, a resin composition including: an alternating copolymer formed of isobutene and N-methylmaleimide; and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion molded product of the resin composition. Any appropriate pressure-sensitive adhesive layer or adhesive layer is used in the lamination of the polarizer and the protective film. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive. The adhesive layer is typically formed of a polyvinyl alcohol-based adhesive.

A-3. Other Layer

A layer having any appropriate function may be formed as the other layer to be arranged between the polarizer and the pressure-sensitive adhesive layer in accordance with an application. Examples of the other layer include: the above-mentioned anchor layer; the protective film to be applied to the polarizer; an adhesive layer; another pressure-sensitive adhesive layer free of any coloring matter; a retardation layer; a light-scattering layer; a light-emitting layer; an undercoat layer; and a liquid crystal layer.

A-4. Substrate

As described above, in one embodiment, the separator to be arranged for protecting the pressure-sensitive adhesive layer is used as the substrate until the polarizing film with a pressure-sensitive adhesive layer is used.

Examples of a constituent material for the separator include: plastic films, such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials, such as paper, cloth, and a nonwoven fabric; and thin-leaf bodies, such as a net, a foam sheet, metal foil, and a laminated body thereof. Of those, a plastic film is suitably used because of its excellent surface smoothness.

The plastic film is not particularly limited as long as the film can protect the pressure-sensitive adhesive layer, and examples thereof include a polyvinyl alcohol film, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film. In one embodiment, a polyvinyl alcohol film, a polyethylene terephthalate film, a film that has been subjected to aluminum deposition, a polyacrylonitrile film, or an ethylene vinyl alcohol film is used as the separator. Each of those films is advantageous because of its low oxygen permeability.

The thickness of the separator is, for example, from 5 μm to 200 μm (preferably from 5 μm to 100 μm, more preferably from 10 μm to 100 μm, still more preferably from 25 μm to 75 μm). The separator may be subjected to release and anticontamination treatments with, for example, a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based release agent, or silica powder, or an antistatic treatment of, for example, an application type, a kneading type, or a vapor deposition type as required. In particular, when the surface of the separator is subjected to a release treatment, such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment, the peelability of the separator from the pressure-sensitive adhesive layer can be further improved.

In one embodiment, a glass film is used as the substrate.

Any appropriate glass film may be adopted as the glass film. According to classification based on composition, examples of the glass film include soda-lime glass, borate glass, aluminosilicate glass and quartz glass films. In addition, according to classification based on an alkali component, examples of the glass film include alkali-free glass and low-alkali glass films. The content of an alkali metal component (e.g., Na₂O, K₂O, Li₂O) in the glass is preferably 15 wt % or less, more preferably 10 wt % or less.

The glass film has a thickness of 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 35 μm or less. The lower limit of the thickness of the glass film is preferably 5 μm or more.

The glass film preferably has a light transmittance at a wavelength of 550 nm of 85% or more. The glass film preferably has a refractive index at a wavelength of 550 nm of from 1.4 to 1.65.

The glass film has a density of preferably from 2.3 g/cm³ to 3.0 g/cm³, more preferably from 2.3 g/cm³ to 2.7 g/cm³. When the glass film has a density falling within the range, an optically functional film can be obtained.

Any appropriate method may be adopted as a forming method for the glass film. The glass film is typically produced by melting a mixture containing a main raw material, such as silica or alumina, a fining agent, such as salt cake or antimony oxide, and a reducing agent, such as carbon, at a temperature of from 1,400° C. to 1,600° C., and forming the molten mixture into a thin sheet shape, followed by cooling. Examples of the forming method for the glass film include a slot down-draw method, a fusion method, and a float method. The glass film formed in a sheet shape by any one of those methods may be chemically polished with a solvent, such as hydrofluoric acid, as required, in order to reduce its thickness or enhance its smoothness.

A commercial glass film may be used as it is as the glass film, or the commercial glass film may be polished into a desired thickness before use. Examples of the commercial glass film include: “7059”, “1737”, or “EAGLE 2000” manufactured by Corning; “AN100” manufactured by Asahi Glass Co., Ltd.; “NA-35” manufactured by NH Techno Glass; “OA-10” manufactured by Nippon Electric Glass Co., Ltd.; and “D263” or “AF45” manufactured by Schott AG.

The substrate has an oxygen permeability of preferably 1 [cm³/(m²·24 h·atm)] or less, more preferably 0.8 [cm³/(m²·24 h·atm)] or less, still more preferably 0.6 [cm³/(m²·24 h·atm)] or less, particularly preferably 0.5 [cm³/(m²·24 h·atm)] or less. When the oxygen permeability falls within such range, a polarizing film with a pressure-sensitive adhesive layer whose pressure-sensitive adhesive layer is excellent in durability can be obtained. The oxygen permeability may be adjusted by, for example, a material forming the substrate or the thickness of the substrate. The oxygen permeability may be measured under the conditions of 23° C. and 0% RH in conformity with JIS K 7126-2.

B. Liquid Crystal Panel

In one embodiment, the polarizing film with a pressure-sensitive adhesive layer is bonded to at least one surface of a liquid crystal cell via the pressure-sensitive adhesive layer of the polarizing film with a pressure-sensitive adhesive layer to form a liquid crystal panel. The polarizing film with a pressure-sensitive adhesive layer of the present invention is suitably used for the viewer side of the liquid crystal cell.

Although a liquid crystal cell of any type, such as a TN type, a STN type, a n type, a VA type, or an IPS type, may be used as the liquid crystal cell, a liquid crystal cell of an IPS mode is suitably used in the liquid crystal panel of the present invention.

The liquid crystal panel may include any other optical layer in addition to the polarizing film. Although the other optical layer is not particularly limited, examples thereof include a reflective plate, a semi-transmissive plate, a retardation plate (including a wavelength plate, such as a λ/2 plate or a λ/4 plate), a viewing angle compensation film, and a brightness enhancement film.

C. Liquid Crystal Display Apparatus

The liquid crystal panel is used in a liquid crystal display apparatus, and the apparatus is formed by, for example, appropriately assembling a constituent part, such as a lighting system, as required, and incorporating a driver circuit into the part. Further, at the time of the formation of the liquid crystal display apparatus, one or two or more appropriate parts, such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light-diffusing plate, and a backlight, may be arranged at appropriate positions. An appropriate liquid crystal display apparatus, such as a liquid crystal display apparatus using a backlight or a reflective plate in its lighting system, may be formed.

EXAMPLES

Now, the present invention is specifically described by way of Examples. However, the present invention is by no means limited by these Examples. Methods of measuring the respective characteristics are as described below.

[Evaluation]

(1) Measurement of Weight-Average Molecular Weight of (Meth)Acrylic Polymer

The weight-average molecular weight (Mw) of a (meth)acrylic polymer was measured by gel permeation chromatography (GPC). The Mw/Mn thereof was also measured in the same manner.

-   -   Analysis device: HLC-8120GPC manufactured by Tosoh Corporation     -   Column: G7000HXL+GMHXL+GMHXL manufactured by Tosoh Corporation     -   Column size: 7.8 mmφ×30 cm each, total: 90 cm     -   Column temperature: 40° C.     -   Flow rate: 0.8 mL/min     -   Injection amount: 100 μL     -   Eluent: tetrahydrofuran     -   Detector: differential refractometer (RI)     -   Standard sample: polystyrene

(2) Measurement of Oxygen Permeability

An oxygen permeability was determined with an oxygen permeability-measuring apparatus OX-TRAN manufactured by Mocon, Inc. under the conditions of 23° C. and 0% RH in conformity with JIS K 7126-2.

(3) Color Deterioration Evaluation

A sample was cut into a test piece measuring 50 mm long by 26 mm wide, and then the states (initial) of its front surface and end portion were captured as an image with a scanner (available under the product name “PIXUS MX923” from Canon Inc.). Next, a durability test in which the sample was left to stand in a thermostat at 80° C. for 15 hours was performed, and then the sample was removed and returned to room temperature (23° C.). After that, the states (15 hours) of the front surface and end portion of the sample were captured as an image with the same scanner again. The photographs before the sample was subjected to the test (initial) and after the standing for 15 hours were binarized. The distance of the longest site of a portion in the peripheral end portion of the test piece where a color was clearly lost in a direction from the peripheral end portion to the center of the test piece was measured with a ruler, and the distance was evaluated as decoloring (color deterioration-advancing distance: mm).

(4) Transmittance Change

The transmittance of the test piece before being subjected to the durability test of the (3) and the transmittance thereof after having been left to stand for 24 hours were measured by using a spectral transmittance-measuring device with an integrating sphere (DOT-3C manufactured by Murakami Color Research Laboratory Co., Ltd.), and a transmittance change ratio was determined.

Example 1 <Production of Polarizing Film>

To produce a thin polarizing layer, first, a laminate having a 9-micrometer thick PVA layer formed on an amorphous PET substrate was subjected to in-air auxiliary stretching at a stretching temperature of 130° C. to produce a stretched laminate. Next, the stretched laminate was dyed to produce a colored laminate. Further, the colored laminate was stretched in boric acid water at a stretching temperature of 65° C. so that a total stretching ratio became 5.94 times. Thus, an optical film laminate including a 4-micrometer thick PVA layer stretched integrally with the amorphous PET substrate was produced. Such two-stage stretching was able to produce an optical film laminate including the 4-micrometer thick PVA layer forming a high-functionality polarizing layer having the following features: the PVA molecules of the PVA layer formed on the amorphous PET substrate were aligned in a high order; and iodine adsorbed by the PVA molecules through the dyeing was aligned as a polyiodide ion complex in one direction in a high order. Further, while a polyvinyl alcohol-based adhesive was applied to the surface of the polarizing layer of the optical film laminate, a 40-micrometer thick acrylic resin film subjected to a saponification treatment (oxygen permeability: 5 [cm³/(m²·24 h·atm)]) was bonded to the surface, followed by the peeling of the amorphous PET substrate. Thus, a polarizing film using a thin polarizer (oxygen permeability: less than 0.02 [cm³/(m²·24 h·atm)]) was produced.

<Preparation of (Meth)Acrylic Polymer>

A monomer mixture containing 100 parts by weight of butyl acrylate, 0.01 part by weight of 2-hydroxyethyl acrylate, and 5 parts by weight of acrylic acid was loaded into a reaction vessel including a condenser, a nitrogen-introducing tube, a temperature gauge, and a stirring apparatus. Further, 0.1 part by weight of 2,2′-azobisisobutyronitrile serving as a polymerization initiator was loaded into 100 parts by weight of the monomer mixture together with 100 parts by weight of ethyl acetate. While the mixture was gently stirred, a nitrogen gas was introduced into the vessel to purge air in the vessel with nitrogen. After that, the temperature of the liquid in the reaction vessel was kept at around 55° C., and a polymerization reaction was performed for 8 hours to prepare a solution (solid content concentration: 30 wt %) of an acrylic polymer having a weight-average molecular weight (Mw) of 1,800,000 and an Mw/Mn of 4.1.

(Preparation of Pressure-Sensitive Adhesive Composition)

100 Parts by weight of the solid content of the acrylic polymer solution produced in the foregoing was compounded with 0.3 part by weight of benzoyl peroxide (available under the product name “NYPER BMT” from Nippon Oil & Fats Co., Ltd.), 1 part by weight of an isocyanate-based cross-linking agent (available under the product name “CORONATE L” from Tosoh Corporation), and 0.25 part by weight of a squaraine compound represented by the following general formula (I-20) to provide a pressure-sensitive adhesive composition.

The squaraine compound represented by the general formula (I-20) was synthesized by the following method.

<Synthesis of Squaraine Compound>

1-Phenyl-1,4,5,6-tetrahydrocyclopenta[b]pyrrole was synthesized by a method described in “M. Beller et. al., J. Am. Chem. Soc., 2013, 135(30), 11384-11388”.

300 Milligrams of 1-phenyl-1,4,5,6-tetrahydrocyclopenta[b]pyrrole and 80 mg of squaric acid were mixed in 5 mL of ethanol, and the mixture was stirred at 80° C. for 2 hours. After that, the mixture was cooled to room temperature, and the product was filtered out. The product that had been filtered out was washed with ethanol, and was dried under reduced pressure at 70° C. to provide 197 mg of a squaraine compound. Further, the compound was purified by silica gel chromatography to provide 120 mg of a squaraine compound.

(Production of Polarizing Film with Pressure-Sensitive Adhesive Layer)

The pressure-sensitive adhesive composition was uniformly applied to the surface of the polarizer (PVA layer) of the thin polarizing film with an applicator in a direct manner, and was dried in an air circulation-type thermostatic oven at 155° C. for 2 minutes to form a 20-micrometer thick pressure-sensitive adhesive layer including a coloring matter (absorption maximum wavelength: 594 nm) on the surface of the polarizer. Thus, a polarizing film with a pressure-sensitive adhesive layer was obtained. The resultant polarizing film with a pressure-sensitive adhesive layer was subjected to the evaluations (3) and (4). The results are shown in Table 1.

Example 2

A polarizing film with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1 except that another pressure-sensitive adhesive layer having a thickness of 25 μm was formed between the polarizer and the pressure-sensitive adhesive layer.

The other pressure-sensitive adhesive layer was formed by transferring, onto the polarizer, an applied layer formed by applying a pressure-sensitive adhesive composition obtained as follows to the PET substrate: 0.3 part by weight of benzoylperoxide (available under the product name “NYPER BMT” from Nippon Oil & Fats Co., Ltd.) and 1 part by weight of an isocyanate-based cross-linking agent (available under the product name “CORONATE L” from Tosoh Corporation) were added to 100 parts by weight of the solid content of the acrylic polymer solution prepared in Example 1.

The resultant polarizing film with a pressure-sensitive adhesive layer was subjected to the evaluations (3) and (4). The results are shown in Table 1.

Comparative Example 1

A polarizing film with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 2 except that the thickness of the other pressure-sensitive adhesive layer was changed to 75 μm. The resultant polarizing film with a pressure-sensitive adhesive layer was subjected to the evaluations (3) and (4). The results are shown in Table 1.

TABLE 1 Distance from Color Trans- polarizer to deterioration mittance pressure-sensitive evaluation <decoloring change adhesive layer (μm) in end portion> (mm) (%) Example 1 0 1 5 Example 2 25 3 9 Comparative 75 13 11 Example 1

As is apparent from Examples and Comparative Example, according to the present invention, when the distance between the polarizer and the pressure-sensitive adhesive layer is set to 25 μm or less, the polarizing film with a pressure-sensitive adhesive layer that is excellent in durability while including the pressure-sensitive adhesive layer having a specific absorption characteristic can be obtained.

Reference Example 1

A polarizing film with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1 except that: a tetraazaporphyrin-based coloring matter (manufactured by Yamamoto Chemicals, Inc., product name: “PD-320”, having a maximum absorption wavelength at a wavelength of 595 nm) was used instead of the squaraine compound represented by the general formula (I-20); and another pressure-sensitive adhesive layer having a thickness of 69 μm was formed between the polarizer and the pressure-sensitive adhesive layer. The composition of the other pressure-sensitive adhesive layer was set to be the same as that of Example 2.

The resultant polarizing film with a pressure-sensitive adhesive layer was subjected to the following evaluation. As result, the result of the color deterioration evaluation was 6.9 mm.

The result shows that in the case where the conventional coloring matter is used, even when the distance from the polarizer to the pressure-sensitive adhesive layer is long, the degree of the color deterioration of the coloring matter is small as compared to that in the case where the squaraine compound is used.

<Color Deterioration Evaluation in Reference Example>

The sample was cut into a test piece measuring 50 mm long by 26 mm wide, and then the states (initial) of its front surface and end portion were captured as an image with a scanner (available under the product name “PIXUS MX923” from Canon Inc.). Next, a durability test in which the sample was left to stand in a thermostat at 85° C. for 24 hours was performed, and then the sample was removed and returned to room temperature (23° C.). After that, the states (after 24 hours) of the front surface and end portion of the sample were captured as an image with the same scanner again. The photographs before the sample was subjected to the test (initial) and after the standing for 24 hours were binarized. The distance of the longest site of a portion in the peripheral end portion of the test piece where a color was clearly lost in a direction from the peripheral end portion to the center of the test piece was measured with a ruler, and the distance was evaluated as decoloring (color deterioration-advancing distance: mm).

INDUSTRIAL APPLICABILITY

The polarizing film with a pressure-sensitive adhesive layer of the present invention is suitably used in an image display apparatus, such as a liquid crystal display apparatus.

REFERENCE SIGNS LIST

-   10 polarizer -   20 pressure-sensitive adhesive layer -   30 another layer -   40 protective film -   50 substrate -   100, 100′, 100″ polarizing film with pressure-sensitive adhesive     layer 

1. A polarizing film with a pressure-sensitive adhesive layer, comprising: a polarizer; and a pressure-sensitive adhesive layer arranged on at least one side of the polarizer, wherein a distance between the polarizer and the pressure-sensitive adhesive layer is 25 μm or less, wherein the pressure-sensitive adhesive layer has an absorption peak in a wavelength band in a range of from 580 nm to 610 nm, and wherein the pressure-sensitive adhesive layer contains a compound X represented by the following general formula (I) or general formula (II):

in the formula (I), R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), R₁ and R₂ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₃, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), R₂ and R₃ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₄, R₅, R₆, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), R₅ and R₆ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₁, R₂, R₃, R₄, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), R₆ and R₇ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₂, R₃, R₄, R₅, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), R₁ and R₂ form a saturated cyclic skeleton including 5 or 6 carbon atoms, R₅ and R₆ form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R₃, R₄, R₇, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), or R₂ and R₃ form a saturated cyclic skeleton including 5 to 7 carbon atoms, R₆ and R₇ form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R₁, R₄, R₅, and R₈ each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b); and in the formula (II), R₄ and R₈ each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms.
 2. The polarizing film with a pressure-sensitive adhesive layer according to claim 1, wherein the polarizer is a polyvinyl alcohol-based polarizer.
 3. The polarizing film with a pressure-sensitive adhesive layer according to claim 1, wherein the polarizer and the pressure-sensitive adhesive layer are directly laminated.
 4. The polarizing film with a pressure-sensitive adhesive layer according to claim 1, wherein the polarizer has an oxygen permeability of 1 [cm³/(m²·24 h·atm)] or less.
 5. The polarizing film with a pressure-sensitive adhesive layer according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 25 μm or less.
 6. An image display apparatus, comprising the polarizing film with a pressure-sensitive adhesive layer of claim
 1. 